Photographic developer



Fatented @el. l'l,

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WILI-IELM DIE'IERLE, or seventeen. NEAR s 'rn'rrean'r, GERMANY.

PHOTOGBAPl-IIG DEVELOPER.

No Drawin 3'.

To aiZ whom i/z may concern: 0

Be it known that I, Wiminmr Dmrnnnn, a subject of the RepublicofVVurtemberg, in Germany, residing at Feuerbach, near tituttgart,Germany, have invented certain new and useful Improvements l11-Pl10tOgraphic Developers (tor which I have filed applications in Germany,patent issued under No. 327,111, filed on Oct. 24, 1918; additionalpatent issued under No. 328,617, filed on Dec. 10, 1918; additionalpatent issued under No. 333,687, filed April 18, 1920 Austriaapplication filed Oct. 142-, 1920; Switzerland application G 7695 filedon Aug. 18, 1920; France application 134,982 filed Oct. 11, 1920;Belgium application 232,860 filed Sept. 25, 1920; Italy application 39?50 filed Sept. 10, 1920; Czecho- Slovakia application P 7680 filed Sept;29, 1920; Sweden application No 4614 filed Sept. 11, 1920; Englandapplication 32883 filed Nov. 22, 1920), of which the following is aspecification.

In the course of experiments to determine the influence of substitutesfor the nucleus or basic constituent of the familiar amidophenol oramidocresol-developers on, their developing properties, I havediscovered that the accession of the carboxyl group and of thesulpho-acid group completely nullifies the developing capacity of thebasic substances so long as the operations are carried out, according tothe known practice, with sodium sulphite and sodium carbonate orpotassium carbonate. By dissolying the developer in water and addingpotassium carbonate, the carboxyland sulpho-acid groups are certainlyconverted into their alkaline salts, but this procedure does not resultin the production of a developing solution. In order to restore thesolutions containing carboxyls or sulphoacids their original developingproperties. the hydroxyl-- groups are, according to this invention, alsomore or less completely converted into their alkaline salts by theapplication of tree caustic alkali. Only thereupon are the developingproperties, which the presence of the carboxyl or sulpho-acid-groups hadnullified, again restored, but they are then re-established in aradically different manner and, as it were, in an improved degree as ishereinafter mentioned. It only a part of the hydroxyl groups present,say 25%,

Application filed March 25, 1921. Serial No. 455/191.

be neutralized with free alkali, a slow actmg developer is produced,whilst, it on the other hand, say 50% of the hydroxyl groups present beneutralized, the developer produced is normal in its action, while thecomplete neutralization of the hydroxyl groups serves to impart to thedeveloper the characteristic of rapid action. Broadly spealc ing,therefore, the carboxylor the sulphoacld group forms, in a certainsense, a means of predetermining and regulating the de velopingproperties of the solution as regards their speed of action.

Moreover, seeing that other favourable qualities from the point of viewof technical photography are attained, the accession of the hydroxylorsulpho-acid groups produces valuable advantages and constitutes a greatadvance in relation to the developers hitherto made use of. Particularlyis this the case as regards the power of my improved developers ofcompensating for the most diverse defects of exposure, more particularlyfor highly excessive exposure which may now be allowed to mount toseveral hundred-fold of the normal. These are advantages affecting thetyro, the skilled amateur or the professional photographer, for even theformer, however defective the exposure, may still obtain reasonablysatis Iactory effects which, with any other developers, would infalliblyhave resulted in unmarketable goods, whilst the latter will be able tocope with problems in photography, which, with the resources hitherto athis disposal, were utterly insoluble.

Further advantages in technical photography are attained by the use ofthis invention: For example, my improved developers show no tendency toindistinct or fogg i cilects, not even to the yellow stain hithertoinvariably resulting from prolonged developinent. The negatives may bereduced. in the usual manner, by ammonium persulphate. According to thedegree of dilution of the developing solution, the silver precipitateexhibits a colour varying from black to brown, a special valuableproperty for diapositive photographs or those taken by gas-light.Potassium bromide furnishes an extensive scale of reducing when usedwith my improved developers. The latter cause no discolouration of thehands and possess all the advantages and none of the disad-.

Normal [ya 0 vantages of the popular pyrogallol developers.

The following examples are taken from. the amidosalicylic acids treatedWithihy drochloric acid A stock solution of lllYl'OClllOl'iLtGtlltlQUlOsalicylic-acid of a tivoor three-told degree on concentration may bepreparedun: the following proportions: I l lydrochloratedparamidosalicylic-acid 100 gm. Sodium sulphite, free from water 500 gm.

fold stl'ul1; 'th (200 gins. sodium hydrate aOHin1iter) 210cc." Water W4790 cc.

Five litres of a 'stoclrsolutions: which may be preserved indefinitely;are 't-husvpro-* duced.= -For develo ainpr: auraoses' this solution isdiluted with an equal. or upto 1 a double volumeof water and thenreacted onyaccording to requirements with the fol lowing proportions ofordinary sodium hy drate SOlUtlOlI-i Solution 1. For anillumination'above the average anddor 3 cc. 1/n NaOH represents asolution of gms. NaOH in a liter of Water.

. For a normal illumination and quicker action;

S. cc. aq. 50cc: l/n NaOH '5 cc.

S. 50 cc. aq. 50 cc. 1/n NaOH 7 cc.

. Fo'r a sparse illumination a11d.rapid acii0n S. 50 cc. aq. 50 cc.1/nNaOH 8 cc.

. For e11largen1ents;=with normal action 5. '50V 00. aqm50 cc. 1/11NuOI-I 10 cc.

6. For enlargements; with quick action; S. 50 cc.

Accordil'igto requirements, these proper.

ma acre tions may be stillfurt-her varied for specialpurposes. If thesolution be, for eX- ample more strongly diluted the result is a slower"development Wltl1"l)l0W11"1701168.

From gradual neutralization,v alter rep eated developing, the sodiumhydrate becomes exhausted of its reactive properties andmust,-therefore, be restored by addition from time totimey so that: thedeveloping solution may recover its original efficacy.

The sodium hydrate is neutralized, i. e., converted into sodiumcarbonate and carbonate-otsodauand, consequently, made ineliicient bythe bromic hydraoid, Which created du ring theeprocess of thedevelopment as Well as by the carbonic acid of the air. Thisneutralization of Ithe 'sodi um i h yd rate goes on much more' rapidlytha-nithe consumption 0mm 'amidosalicylic acid by the;

It: is for this 1 reason:- thatthe developer may repeatedly beregendevelopment itself.

erated throng-litheaddition ot sodium hydrate', until it will graduallybecome inefli the carboand sulphoecids of an H.1n'1tl0-- phenol-ora'homolgue of the same 111 caust1e.v alkal l solution;

In testimony whereofl my signature in presence of two Witnesses.

' DinWVII-JHELM D:[lTKlTERLlJi l/Vitnesses.

El SOHLEIOHER, FBIEDA KLAIBES;

